OpenWrt 18.06 RC2 Dmesg message (urandom, lack of entropy)


Running OpenWRT 18.06 RC2 on x86/x64 machine, there is strange message at the end of dmesg log after booting.

 [  176.262358] random: crng init done
 [  176.262665] random: 1 urandom warning(s) missed due to ratelimiting

Any idea what it could be?
Everything seems to be working fine.

Many thanks,

1 Like

Urandom needs some data to seed itself, try typing on the keyboard during boot give it more data


It's really curious (the "solution" I mean).

Welcome to the magic world of entropy

[    0.037905] random: get_random_u32 called from bucket_table_alloc+0x1a4/0x1f8 with crng_init=0
[    5.369145] random: procd: uninitialized urandom read (4 bytes read)
[    9.282518] urandom-seed: Seeding with /etc/urandom.seed
[    9.994960] random: ubusd: uninitialized urandom read (4 bytes read)
[   10.005219] random: ubusd: uninitialized urandom read (4 bytes read)
[   10.011859] random: ubusd: uninitialized urandom read (4 bytes read)
[   11.759376] urandom_read: 5 callbacks suppressed
[   11.759383] random: jshn: uninitialized urandom read (4 bytes read)
[   24.762525] random: fast init done
[   57.390892] random: crng init done


All this "improvements/changes" have been introduced in 4.14.XX Kernels?
Because I don't remember messages like that in older firmwares (Lede/OpenWRT 4.9.XXX).

You will see this messages also on 4.9, 4.4 and probably older kernel versions too.

Thanks @juppin I never realized about this messages before.

Lack of entropy is a real problem in embedded devices right after boot.

I think that the warning for urandom quality was added to the kernel some time ago, but the warning was modified just a few months ago: and backport to 4.9:

You might read Randomness quality for some background on lack of entropy in Openwrt. I wrote there a brief summary of mitigation attempts in Openwrt in the last 5-6 years.